<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        div{
            width: 200px;
            height: 200px;
            border-top: 20px solid red;
            border-right: 20px solid blueviolet;
            border-left: 20px solid yellow;
        }
    </style>
<body>
<div>

</div>

</body>
</html>